Question

1²-a²-b²+2ab
Factorise

Answer 1

$1 - a {}^{2} - b {}^{2} + 2ab = 0 \\ - 1 + a { }^{2} + b {}^{2} - 2ab = 0 \\ - 1 + (a - b) {}^{2} \\ = (a - b) {}^{2} = 1 \\ (a - b) = \frac{ + }{ - } 1$